Background: We present a novel block of the articular branch of the femoral nerve (ABFN) and anterior obturator (AO) nerve for perioperative analgesia during various hip surgeries. Materials and Methods: In this prospective audit, 30 patients underwent hip surgeries such as hemiarthroplasty, percutaneous femoral nailing, and dynamic hip screwing performed by the same surgeon under subarachnoid block (SAB) that was performed by the same anesthesiologist using 10–15 mg of bupivacaine 0.5% (heavy). Pain management after hip surgery used to be provided by using epidural analgesia or intravenous (IV) analgesia. During this study, we performed ultrasonography (USG)-guided block to ABFN and AO with injection ropivacaine (0.2%) 35 mL (20 + 15 mL) with 8 mg dexamethasone just before spinal anesthesia in operation theatre. Pain scores were compared using Numeric Pain Rating Scale at pre-procedure, followed by 0, 4, 8, and 12 h after the block and the requirement of first dose of IV analgesics. Results: Pain scores were significantly lower in these patients in the first 12 h of the surgery along with less requirement of IV analgesics. The onset of blocks start within 3–5 min, and patients were more comfortable in sitting position while performing SAB. Discussion: Blocking ABFN and AO nerve provides superior analgesia during perioperative period in hip surgeries and decreases the requirements of IV analgesics and provides effective analgesia in patients while performing SAB in sitting position.

With an increasing number of hip surgeries, such as hemiarthroplasty, percutaneous femoral nailing (PFN), and dynamic hip screwing (DHS), leading to severe postoperative pain, where an intraoperative anesthesia is mostly subarachnoid block (SAB), there is a controversy about the choice of postoperative analgesia. Epidural analgesia is interfered by thromboprophylaxis, whereas intravenous (IV) analgesics can cause nausea, vomiting, drowsiness, giddiness, gastritis, ulceration, hemorrhage, and so on.

The nerve supplies of femoral head are articular branch of femoral nerve (ABFN) and hip articular branch of anterior obturator (AO) nerve. When blocked by ultrasonography (USG) guidance, they improve perioperative pain control and reduce IV analgesic requirements without hampering motor activity. These blocks also help to reduce pain before giving SAB, which allows the patient to sit comfortably.

Materials and Methods

Thirty patients were included in this prospective study after having obtained approval by the institutional review board for chart review. The patients were scheduled for hemiarthroplasty, PFN, and DHS from May 2017 to September 2017 (n = 30). The same surgical team performed all the operations. No changes were made in the surgical technique or protocols during the study period, and the average duration of all surgeries was around 2–2.5 h and total duration of SAB was approximately a maximum of 2 h and 45 min. The same anesthesiologist using USG performed all peripheral nerve blocks.

Routine anesthetic monitoring was conducted in the operating room using noninvasive blood pressure (NIBP), peripheral oxygen saturation, and continuous electrocardiography with heart rate. ABFN and AO nerve USG-guided blocks were given before spinal anesthesia to reduce pain, which made the patients sit comfortably during SAB.

Imaging of the inguinal region was performed in each subject by using a linear 10 to 5 MHz ultrasound probe. First, the femoral artery is visualized in short axis, the probe is then moved laterally for 3–4 cm along the sartorius muscle, 3–4 cm inferior to the inguinal ligament. The ABFN is then recognized as a white triangular to oval-shaped area (0.5–1 cm) surrounded by sartorius superiorly, rectus femoris laterally, and iliacus medially [Figure 1].{Figure 1}

After sterile preparation, 40 mL 0.2% ropivacaine and 2 mL (8 mg) dexamethasone were taken. Then, a 1.5” long 22G hypodermic needle with 10 cm extension was directed (after de-airing) under USG guidance (out of plane technique) targeting the ABFN and a 20 mL of drug mixture was injected through the needle, visualizing the nerve and lifting the sartorius muscle by the drug. After giving ABFN block, the USG probe was relocated to femoral artery and moved medially to locate AO nerve, which runs in between the adductor longus (AL) and adductor brevis (AB) muscles.

After identifying AO nerve, the same needle was placed under USG guidance (out-of-plane technique) targeting the nerve between AL and AB muscles, and 15 mL mixture of 0.2% ropivacaine and dexamethasone was injected through the needle visualizing the AO nerve surrounded by LA and separating the fascia between AL and AB [Figure 2].{Figure 2}

Later, all patients received spinal anesthesia in standard manner (L2-L3) using 12.5 mg (2.5 mL) of 0.5% Sensorcaine Hyperbaric (H) during surgery and total duration of anesthesia was 2 h and 45 min approximately.

Postoperatively, the patients were monitored for return of pain at the surgical site. Pain scores were assessed using a Numeric Pain Rating Scale (0–10 with 0 being no pain at all and 10 being the worst imaginable pain) and recorded at an interval of 0, 4, 8, and 12 h after the block. It was made sure that the sensory and motor effect of spinal anesthesia has worn off. Along with the pain score, patient's vitals such as heart rate (HR) and NIBP levels were measured and recorded in the following intervals. The time interval between the block and first analgesic administration according to hospital protocol was recorded.

The data of patients were compared and statistically analyzed using Statistical Package for Social Science software (IBM SPSS Statistics) for Microsoft Windows. In the entire study, the P values less than 0.05 were considered to be statistically significant.

Results

Thirty cases were studied in which 15 patients were male and 15 were female and the age distribution was 35–85yrs. The surgeries mainly performed were hemiarthroplasty, DHS, and PFN. The mean onset of the block was 3.5 min. The pain scores (visual analog scale [VAS]) at pre-block and post-block were studied, and it was found that the distribution of pre-block mean pain score (VAS) was significantly higher compared to post-block mean pain score at 0, 4, 8, and 12 h of follow-up time intervals (P < 0.001 for all) [Figure 3]. The minimum to maximum duration of first rescue analgesia after administration of block was 11–18 h. The mean ± standard deviation of duration of first rescue analgesia after administration of block was 13.27 ± 1.69 h.{Figure 3}

This block also helps in maintaining the hemodynamic stability postoperatively. The distribution of pre-block mean HR was significantly higher compared to mean HR at 0, 4, 8, and 12 h of post-block follow-up time intervals (P < 0.001 for all) [Figure 4].{Figure 4}

Twelve hours after surgery, all patients were tested and they could mobilize the operated limb, no impairment in the form of paresthesia because of the ABFN and AO nerve block was noted.

Discussion

We present a novel method of pain treatment after surgery (hemiarthroplasty, DHS, and PFN) via USG-guided ABFN[1] and AO nerve block. The aim of this study was to help the patient comfortably sit, pain free before spinal anesthesia and reduce the use of IV analgesics during postoperative period for a minimum of 12 h and a maximum of 18 h. Blocking the sensory innervations of hip by blocking these nerves is an effective method of pain treatment immediately following hip surgery.

Epidural analgesia is frequently administered to provide analgesia after hip surgery,[7] though this method provides good analgesia, the drawbacks are as follows:

Sitting position for epidural is very painful in these patients and procedure becomes difficult and time consuming due to inadequate positionEpidural analgesia was associated with a greater incidence of urinary retention and hypotension[3]Sometimes it causes significant concomitant motor blockade and a significant risk of epidural hematoma, which is a rare but potentially disastrous complication concerning patients who receive post-op thromboprophylaxis[8],[9],[10]

Peripheral nerve blocks provide analgesia similar to epidural analgesia with a more specific nerve block and immediate action and are superior to systemic analgesia for pain relief.[11] Peripheral nerve blocks preserve contralateral limb strength that may facilitate postoperative rehabilitation when compared with the bilateral lower extremity motor block often seen with epidural analgesia.[8]

Several authors have advocated the use of lumbar plexus block with or without sciatic nerve block,[12],[13] femoral nerve block,[14] and fascia iliaca block[15],[16],[17] following hip surgery. Two studies showed that posterior lumbar plexus block did cause better analgesia than placebo, whereas femoral block was not able to provide any significant pain relief. Despite these advantages, the placement of lumbar plexus and sciatic nerve block requires advanced skill along with changing of patient position prone or lateral, which is painful and time-consuming and they can cause serious potential side effects including patients' fall and injury,[18] nerve injury,[12] neuraxial block, systemic absorption of LA, and retroperitoneal hematoma.[19],[12]

Locating ABFN and AO nerve in patient via USG is less difficult in supine position as compared to other blocks, which provides great pain relief. The study clearly shows the effectiveness of block in the ABFN and AO nerve just before SAB during hip surgery and superior postoperative analgesia for the same. In our study, 43% patients were completely free of pain till 8 h after block, whereas 20% patients were completely free of pain for 12 h. So, this technique significantly reduced the postoperative pain and administration of IV analgesics for the first 12 h.

Eikelboom JW, Karthikeyan G, Fagel N, Hirsh J. American Association of Orthopedic Surgeons and American College of Chest Physicians guidelines for venous thromboembolism prevention in hip and knee arthroplasty differ: what are the implications for clinicians and patients? Chest 2009;135:513-20.